Plasma Fibrinogen, Carotid Thickness and Flow Mediated Dilation: Influence of Age, Physical Activity and Function

Abstract

Elevated plasma fibrinogen levels have been proposed to act directly on the endothelial wall, resulting in accelerated intima-media thickening and reduced flow mediated dilation. Aging is associated with an increase in plasma fibrinogen levels, but physical activity and fitness appear to play a modifying role. PURPOSE:(1) To examine age-related effects on plasma fibrinogen levels and arterial structure and function, and (2) to determine the possible modifying role of higher physical activity and function. METHODS: Subjects from the Louisiana Healthy Aging Study (n=63; Age: 84±12, 61 to 101years) were used for these analyses. Plasma fibrinogen was analyzed from fasting blood draws. Arterial structure [Carotid-Arterial Mass (C-MASS)] and function [Brachial Artery Flow Mediated Dilation (BAFMD)] were measured using high-resolution Doppler ultrasonography. Physical activity was assessed using the Yale Activity Inventory (YAI), and physical function was measured using the Continuous Scale of Physical Function and Performance (PFP). RESULTS: Plasma fibrinogen [3.31 * (age) + 180.52, r=0.40, p=0.005], CMASS [0.11 * (age) + 3.58, r=0.70, p=0.001], and BAFMD [-0.12 * (age) + 13.89, r=0.44, p=0.002] were significantly associated with age. YAI declined with age [-0.83 * (age) + 109.96, r=0.38, p=0.008], and was strongly associated with physical function [0.57 * (PFP) + 16.55, r=0.46, p=0.001]. Individuals in the highest physical activity and function tertiles had significantly lower plasma fibrinogen (YAI Hi: 421±94, YAI Lo: 503±107, p=0.03; PFP Hi: 409±75, PFP Lo: 503±106mg/dl, p=0.01) and CMASS (YAI Hi: 12.20±2.15, YAI Lo: 13.98±1.53, p= 0.03; PFP Hi: 11.80±75, PFP Lo: 13.75±1.40mm2, p=0.003), and higher BAFMD (YAI Hi: 4.79±3.36, YAI Lo: 2.18±2.88%, p=0.03; PFP Hi: 5.14±3.58, PFP Lo: 2.47±2.69%, p=0.03), compared to those in the lowest tertile. These differences were also apparent in a separate multivariate analysis in nonagenarians, except for CMASS. CONCLUSION: These data confirm significant age-dependent changes in plasma fibrinogen, arterial structure and function. Higher levels of physical activity and function, even in nonagenarians, appear to protect against these age-dependent changes. This research was supported by a grant from the NIA (1 P01 AG022064) (S.M. Jazwinski)